Apparatus and methods for treating hardened vascular lesions

ABSTRACT

An angioplasty catheter comprises a catheter body having a balloon or other radially expansible shell at its distal end. A non-axial external structure is carried over the shell and scores a stenosed region in a blood vessel when the balloon is inflated therein. The catheter has an attachment structure disposed between the catheter body and the balloon to accommodate foreshortening and rotation of the external structure as the balloon is expanded. The external structure may be part of a helical cage structure which floats over the balloon.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part patent application ofcommonly assigned, co-pending U.S. application Ser. No. 10/631,499,filed on Jul. 30, 2003 (Attorney Docket No. 021770-000110US), whichclaims the benefit under 35 USC §119(e) of U.S. Provisional ApplicationNo. 60/442,161, filed on Jan. 21, 2003 (Attorney Docket No.021770-000100US), the full disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to the field of medical devices,more specifically medical to devices intended to treat stenoses in thevascular system.

[0004] Balloon dilatation (angioplasty) is a common medical proceduremainly directed at revascularization of stenotic vessels by inserting acatheter having a dilatation balloon through the vascular system. Theballoon is inflated inside a stenosed region in a blood vessel in orderto apply radial pressure to the inner wall of the vessel and widen thestenosed region to enable better blood flow.

[0005] In many cases, the balloon dilatation procedure is immediatelyfollowed by a stenting procedure where a stent is placed to maintainvessel patency following the angioplasty. Failure of the angioplastyballoon to properly widen the stenotic vessel, however, may result inimproper positioning of the stent in the blood vessel. If a drug-elutingstent is used, its effectiveness may be impaired by such improperpositioning and the resulting restenosis rate may be higher. This is aresult of several factors, including the presence of gaps between thestent and the vessel wall, calcified areas that were not treatedproperly by the balloon, and others.

[0006] Conventional balloon angioplasty suffers from a number of othershortcomings as well. In some cases the balloon dilatation procedurecauses damage to the blood vessel due to aggressive balloon inflationthat may stretch the diseased vessel beyond its elastic limits. Suchover inflation may damage the vessel wall and lead to restenosis of thesection that was stretched by the balloon. In other cases, slippage ofthe balloon during the dilatation procedure may occur. This may resultin injury to the vessel wall surrounding the treated lesion. Oneprocedure in which slippage is likely to happen is during treatment ofin-stent restenosis, which at present is difficult to treat byangioplasty balloons. Fibrotic lesions are also hard to treat withconventional balloons, and elastic recoil is usually observed aftertreatment of these lesions. Many long lesions have fibrotic sectionsthat are difficult to treat using angioplasty balloons.

[0007] An additional problem associated with balloon angioplastytreatment has been the “watermelon seed effect.” Angioplasty is carriedout at very high pressures, typically up to twenty atmospheres orhigher, and the radially outward pressure of the balloon can cause axialdisplacement of the balloon in a manner similar to squeezing awatermelon seed with the fingers. Such axial displacement, of course,reduces the effectiveness of balloon dilatation. Another problem withconventional angioplasty balloon design has been deflation of theballoon. Even after the inflation medium is removed from a balloon, thedeflated configuration will have a width greater than the originalfolded configuration which was introduced to the vasculature. Such anincrease in profile can make removal of the balloon difficult.

[0008] Atherectomy/Thrombectomy devices intended to removeplaque/thrombus material may also include a structure that expands in alesion while the plaque/thrombus removal mechanism is within thisstructure. The removed material is either being stacked in the catheteror sucked out thru the catheter. When the procedure is done, theexpandable structure is collapsed and the catheter removed. Foreignobject removal devices usually include a basket structure that needs tobe expanded to collect the object and then collapse for retrieval.Distal protection devices usually include a basket structure thatsupport a mesh that needs to be expanded distal to the treated lesion tocollect the loose objects and then collapse for retrieval .

[0009] These devices usually include an elastic metallic material thatneeds to be expanded in the vascular system to fulfill its task andafterwards collapse to a small diameter to facilitate retrieval. Thetransition between the collapsed (closed) configuration to the expanded(open) configuration can be done in two ways: the structure can be at anormally closed (collapsed) configuration in which force is applied tocause the structure to expand. In this case, the elastic recoil of thestructure will cause it to collapse back to closed configuration whenthe expanding force ceases. The structure may also be at a normally open(expanded) configuration in which a constraining element is forced overit to hold it dawn for the collapsed configuration (for example aconstraining tube). When this constraining element is removed thestructure is free to expand to the expanded (open) configuration. Thestructure material may also be non elastic. In this case, the structurewill need to be forced to transit between both collapsed and expandedconfiguration.

[0010] One problem associated with conventional angioplasty expansionsystems is that the transition between the collapsed and expandedconfigurations involves significant rotational and axial reactionforces. These reaction forces are applied by the structure on thecatheter as a result of the force applied by the catheter to expand orclose the structure. Axial reaction forces are created due theforeshortening of the structure during expansion. Rotational reactionforces (torques) are created when a non longitudinal element is forcedto expand/collapse. Since the catheters are usually less stiff thestructure, these reaction forces may cause that the structure will notexpand or collapse properly, or cause undesired deformation to thecatheter itself.

[0011] To overcome at least some of these problems these problems, U.S.Pat. No. 5,320,634 describes the addition of cutting blades to theballoon. The blades can cut the lesions as the balloon is inflated. U.S.Pat. No. 5,616,149 describes a similar method of attaching sharp cuttingedges to the balloon. U.S. Patent Publication 2003/0032973 describes astent-like structure having non-axial grips for securing an angioplastyballoon during inflation. U.S. Pat. No. 6,129,706 describes a ballooncatheter having bumps on its outer surface. U.S. Pat. No. 6,394,995describes a method of reducing the balloon profile to allow crossing oftight lesions. U.S. Patent Publication 2003/0153870 describes a balloonangioplasty catheter having a flexible elongate elements that createlongitudinal channels in a lesion or stenosis.

[0012] While the use of angioplasty balloons having cutting blades hasproved to be a significant advantage under many circumstances, thepresent cutting balloon designs and methods for their use continue tosuffer from shortcomings. Most commercial cutting balloon designs,including those available from INTER VENTIONAL TECHNOLOGIES, INC., ofSan Diego, Calif., now owned by BOSTON SCIENTIFIC, of Natick, Mass.,have relatively long, axially aligned blades carried on the outersurface of an angioplasty balloon. Typically, the blades are carried ona relatively rigid base directly attached to the outer balloon surface.The addition of such rigid, elongated blade structures makes the balloonitself quite stiff and limits the ability to introduce the balloonthrough torturous regions of the vasculature, particularly the smallervessels within the coronary vasculature. Moreover, the cutting balloonscan be difficult to deflate and collapse, making removal of the balloonsfrom the vasculature more difficult than with corresponding angioplastyballoons which do not include cutting blades. Additionally, the axiallyoriented cuts imparted by such conventional cutting balloons do notalways provide the improved dilatation and treatment of fibrotic lesionswhich would be desired.

[0013] For these reasons, it would be desirable to provide improvedcutting balloon designs and methods for their use. In particular, itwould be desirable to provide cutting balloons which are highly flexibleover the length of the balloon structure, which readily permit deflationand facilitate removal from the vasculature, and which are effective intreating all forms of vascular stenoses, including but not limited totreatment of highly calcified plaque regions of diseased arteries,treatment of small vessels and/or vessel bifurcations that will not bestented, treatment of ostial lesions, and treatment of in-stentrestenosis (ISR). Moreover, it would be desirable if such balloonstructures and methods for their use could provide for improvedanchoring of the balloon during dilatation of the stenosed region.

[0014] It would further be desirable to minimize the reaction forcesapplied by the external structure to the catheter, and at the same timebe able to control the expansion of the expandable structure. It wouldalso be desirable to adjust the compliance of the system in apredictable way without changing the materials or geometry of theexpandable structure. At least some of these objectives will be met withthe inventions described hereinafter.

[0015] 2. Description of the Background Art

[0016] The following U.S. patents and printed publication relate tocutting balloons and balloon structures: U.S. Pat. Nos.6,450,988;6,425,882; 6,394,995; 6,355,013; 6,245,040; 6,210,392;6,190,356; 6,129,706; 6,123,718; 5,891,090; 5,797,935; 5,779,698;5,735,816; 5,624,433; 5,616,149; 5,545,132; 5,470,314; 5,320,634;5,221,261; 5,196,024; and Published U.S. patent application Ser. No.2003/0032973. Other U.S. patents of interest include U.S. Pat. Nos.6,454,775; 5,100,423, 4,998,539; 4,969,458; and 4,921,984.

SUMMARY OF THE INVENTION

[0017] The present invention provides improved apparatus and methods forthe dilatation of stenosed regions in the vasculature. The stenosedregions will often include areas of fibrotic, calcified, or otherwisehardened plaque or other stenotic material of the type which can bedifficult to dilatate using conventional angioplasty balloons. Themethods and apparatus will often find their greatest use in treatment ofthe arterial vasculature, including but not limited to the coronaryarterial vasculature, but may also find use in treatment of the venousand/or peripheral vasculature, treatment of small vessels and/or vesselbifurcations that will not be stented, treatment of ostial lesions, andtreatment of ISR.

[0018] In a first aspect of the present invention, a scoring cathetercomprises a catheter body having a proximal end and a distal end, aradially expansible shell near the distal end of the catheter body, anda non-axial scoring structure carried over the shell. By “non-axialscoring structure,” it is meant that the structure will be able to scoreor cut stenotic material within a treated blood vessel along lines whichare generally in a non-axial direction. For example, the scoring linesmay be helical, serpentine, zig-zag, or may combine some axialcomponents together with such non-axial components. Usually, thenon-axial scoring pattern which is imparted will include scoringsegments which, when taken in total, circumscribe at least a majority ofand usually the entire inside wall of the blood vessel up to one time,preferably more than one time, usually more than two times, often atleast three times, more often at least four, five, six, or more times.It is believed that the resulting scoring patterns which circumscribesthe inner wall of the vessel will provide improved results duringsubsequent balloon dilatation.

[0019] Usually the scoring structure will comprise at least onecontinuous, i.e., non-broken, scoring element having a length of atleast 0.5 cm, more usually at least 1 cm, often at least 2 cm, usuallyat least 3 cm, and sometimes at least 4 cm or more. Alternatively, thescoring structure may comprise a plurality of much smaller segmentswhich may be arranged in a helical or other pattern over the balloon,typically having a length in the range from 0.1 cm to 2 cm, often being0.5 cm or less, sometimes being 0.3 cm or less.

[0020] In order to promote scoring of the blood vessel wall when theunderlying expansible shell is expanded, the scoring structure willusually have a vessel contact area which is 20% or less of the area ofthe expansible shell, usually being below 10%, and often being in therange from 1% to 5% of the area of the expansible shell. The use of ashell having such a relatively small contact area increases the amountof force applied to the vascular wall through the structure by expansionof the underlying expandable shell. The scoring structure can have avariety of particular configurations, often being in the form of a wireor slotted tube having a circular, square, or other cross-sectionalgeometry. Preferably, the components of the scoring structure willcomprise a scoring edge, either in the form of a honed blade, a squareshoulder, or the like. A presently preferred scoring edge iselectropolished and relatively small.

[0021] In a preferred embodiment, the scoring stricture may be formed asa separate expansible cage which is positioned over the expansible shellof the catheter. The cage will usually have a collar or other attachmentstructure at each end for placement on the catheter body on either sideof the expansible shell. A collar may be a simple tube, and otherattachment structures will usually be crimpable or otherwisemechanically attachable to the catheter body, such as a serpentine orother ring structure. The attachment structures on the cage may beattached at both ends to the catheter body, but will more usually beattached at only a single end with the other end being allowed to floatfreely. Such freedom allows the scoring structure to shorten as thestructure is expanded on the expansible shell. In certain embodiments,both ends of the scoring structure will be fixed to the catheter body,but at least one of the attachment structures will have a spring orother compliant attachment component which provides an axial extensionas the center of the scoring structure foreshortens.

[0022] In many cases, since the scoring elements are non-axial, thereare torques induced during the expansion of the balloon and theshortening of the scoring structure. These torques may be high, and ifone end of the scoring structure is constrained from rotation, thescoring element will not expand properly. The final expandedconfiguration of the scoring element is achieved via shortening androtation.

[0023] In a preferred embodiment, both sides of the scoring element arefixed to the catheter, but at least one side will have a compliantstructure which will provide axial tension and at the same time willallow the scoring element to rotate to its final configuration.

[0024] In some cases both ends of the scoring element are fixed and theshortening is achieved by deformation of the wire. For example, the wirecan have a secondary structure which permits elongation (e.g., it may bea coiled filament) or can be formed from a material which permitselongation, e.g., nitinol. The scoring element can be attached in bothends, in a way that will allow rotation. In the case were the torquesare low (depending on the design of the scoring element) there is noneed for rotation and the torque can be absorbed either be the scoringelement of by the catheter.

[0025] In all cases, the scoring structure is preferably composed of anelastic material, more preferably a super elastic material, such asnitinol. The scoring structure is thus elastically expanded over theexpansible shell, typically an inflatable balloon similar to aconventional angioplasty balloon. Upon deflation, the scoring structurewill elastically close to its original non-expanded configuration, thushelping to close and contain the balloon or other expandable shell.

[0026] In some cases the scoring element will be a combination of morethan one material. In one case the scoring element can be made fromnitinol and parts of it can be made from stainless steel. In other casesthe scoring element can be made of stainless steel or nitinol and partof it can be made from polymer to allow high deformations.

[0027] In other preferred embodiments, the assembly of the shell and thescoring structure will be sufficiently flexible to permit passagethrough tortuous regions of the vasculature, e.g., being capable ofbending at radius of 10 mm or below when advanced through 45°, 90° orhigher bends in the coronary vasculature. Usually, the scoring structurewill comprise one or more scoring elements, wherein less than 70% of thecumulative length of the scoring element is aligned axially on the shellwhen expanded, preferably being less than 50% of the cumulative length,and more preferably being less than 25% of the cumulative length. Inother instances, the scoring structure may comprise one or more scoringelements, wherein the cumulative length of the scoring element includesa non-axial component of at least 10 mm, preferably at least 12 mm, andmore preferably 36 mm. Preferably, at least some of the scoring elementswill have scoring edges which are oriented radially outwardly along atleast a major portion of their lengths at all times during inflation anddeflation and while inflated. By “radially outward,” it is meant that asharp edge or shoulder of the element will be oriented to score or cutinto the stenotic material or the interior wall of the treated vessel,particularly as the shell is being inflated.

[0028] The scoring elements will usually, but not necessarily, have ascoring edge formed over at least a portion of their lengths. A “scoringedge” may comprise a sharpened or honed region, like a knife blade, or asquare shoulder as in scissors or other shearing elements.Alternatively, the scoring elements may be free from defined scoringedges, e.g., having circular or the other non-cutting profiles. Suchcircular scoring elements will concentrate the radially outward force ofthe balloon to cause scoring or other disruption of the plaque or otherstenotic material being treated.

[0029] In a second aspect of the present invention, the scoring cathetercomprises a catheter body and a radially expansible shell, generally asset forth above. The scoring structure will be composed of elementswhich circumscribe the radially expansible shell. By “circumscribing theradially expansible shell,” it is meant that at least some scoringelements of the scoring structure will form a continuous peripheral pathabout the exterior of the expansible shell during expansion. An exampleof such a fully circumscribing structure is a helical structure whichcompletes up to one 360° path about the balloon before, during and afterexpansion, usually completing two complete revolutions, and frequentlycompleting three, four, or more complete revolutions. Exemplary helicalstructures may include two, three, four, or more separate elements, eachof which is helically arranged around the radially expansible shell.

[0030] In a third aspect of the present invention, a scoring cathetercomprises a catheter body and a radially expansible shell, generally asset forth above. An elongated scoring structure is carried over theshell, and the assembly of the shell and the scoring structure will behighly flexible to facilitate introduction over a guide wire, preferablybeing sufficiently flexible when unexpanded so that it can be bent at anangle of at least 90°, preferably 18°, at a radius of 1 cm withoutkinking or otherwise being damaged. Such flexibility can be determined,for example, by providing a solid cylinder having a radius of 1 cm andconforming the assembly of the scoring structure and expansible shellover the cylinder. Alternatively, the assembly can be advanced over aguide wire or similar element having a 180° one centimeter radius bend.In either case, if assembly bends without kinking or other damage, itmeets the requirement described above. Other specific features in thisfurther embodiment of the catheters of the present invention are asdescribed above in connection with the prior embodiments.

[0031] In a fourth aspect of the present invention, a plaque scoringcatheter comprises a catheter body and a radially expansible balloon,generally as set forth above. A plurality of scoring elements aredistributed over the balloon, typically being attached directly to anouter surface of the balloon. The scoring elements will be relativelyshort, typically having lengths below about 25% of the balloon length,preferably having lengths in the range from 2% to 10% of the balloonlength. The relatively short, segmented scoring elements will permithighly flexible assemblies of balloon and scoring elements, generallymeeting the flexibility requirement set forth above. The scoringelements may be arranged randomly over the balloon but will more usuallybe distributed uniformly over the balloon. In specific embodiments, thescoring elements may be arranged in helical, serpentine, or otherregular patterns which circumscribe the balloon. As the balloon expands,such short segments will generally move apart from each other, but willstill impart the desired scoring patterns into the vascular wall as theballoon is inflated.

[0032] In a fifth embodiment, the scoring catheter according to thepresent invention comprises a catheter body and a radially expansibleballoon generally as set forth above. The balloon has a plurality oflobes extending between ends of the balloons, and at least one scoringelement will be formed on at least one of the lobes in a manner arrangedto score stenotic material as the balloon is expanded. The lobe willusually be in a helical pattern, and typically two, three, or more lobeswill be provided. In the case of helical lobes, the scoring element(s)will usually be disposed along a helical peak defined by the helicallobe when the balloon is inflated. Such helical scoring elements will bearranged to accommodate balloon inflation, typically being stretchable,segmented, or the like.

[0033] In still another aspect of the apparatus of the presentinvention, an expansible scoring cage is adapted to be carried over aballoon of a balloon catheter. The scoring cage comprises an assembly ofone or more elongate elastic scoring elements arranged in a non-axialpattern. As defined above, the non-axial pattern may comprise both axialand non-axial segments. The assembly is normally in a radially collapsedconfiguration and is expansible over a balloon to a radially expandedconfiguration. After the balloon is deflated, the assembly returns to aradially collapsed configuration, preferably being assisted by theelastic nature of the scoring cage. Advantageously, the scoring cagewill enhance uniform expansion of the underlying balloon or otherexpansible shell and will inhibit “dog boning” where an angioplastyballoon tends to over inflate at each end, increasing the risk of vesseldissection. The scoring elements will be adapted to score hardenedstenotic material, such as plaque or fibrotic material, when expanded bythe balloon in a blood vessel lumen. The scoring cage may be adapted tomount over the balloon with either or both ends affixed to the balloon,generally as described above in connection with prior embodiments.Preferred geometries for the scoring elements include those whichcircumscribe the balloon, those which are arranged helically over theballoon, those which are arranged in a serpentine pattern over balloonand the like.

[0034] In yet another aspect of the present invention, a method fordilatating a stenosed region in a blood vessel comprises radiallyexpanding a shell which carries a scoring structure. The scoringstructure scores and dilates the stenosed region and includes one ormore non-axial scoring elements arranged to impart a circumscribingscore pattern about the inner wall of the blood vessel as the shell isexpanded. The stenosed region is typically characterized by the presenceof calcified plaque, fibrotic plaque, or other hardened stenoticmaterial which is preferably scored prior to dilatation. Preferably, thescoring structure will not be moved in axial direction while engagedagainst the stenosed region, and the scoring structure may optionally befree from axially scoring elements.

[0035] In still another aspect of the present invention, an angioplastycatheter comprises a catheter body and a radially expansible shell nearthe distal end of the catheter body. An external structure, such as ascoring structure or cutting structure, is carried over but unattachedto the shell. The catheter further comprises an attachment structurehaving a proximal end and a distal end attached to the scoringstructure, wherein the attachment structure is sufficiently sized andcompliant to accommodate reaction forces or geometrical changes producedby the scoring structure as it is expanded by the shell. Generally, atleast a portion of said scoring structure is arranged helically over theshell. However, the scoring structure may comprise numerous differentconfigurations as described above.

[0036] In one aspect of the present invention, the proximal end of theattachment structure is fixed to the catheter body and the distal end ofthe attachment structure is secured to the proximal end of the scoringstructure. In all cases, the attachment structure is capable axially androtationally extending to accommodate foreshortening of the scoringstructure as the shell is expanded.

[0037] In a preferred embodiment, the attachment structure comprises acompliance tube having an outer diameter and an inner diameter thatextends over the catheter body. The inner diameter of the compliancetube is generally larger than an outer diameter of the catheter body sothat the compliance tube freely extends and/or rotates with respect tothe catheter body as the scoring structure foreshortens.

[0038] The compliance tube may also be sized to control the complianceof the scoring structure and expansible shell. Generally, the compliancetube has wall thickness ranging from 0.01 in to 0.1 in. The wallthickness may be increased to lessen the compliance of the system, ordecreased to create a greater compliance. The length of the compliancetube may also be adjusted to control the compliance of the system.Generally, compliance tube has a length ranging from 1 cm to 10 cm, butmay range up to 30 cm or more for embodiments wherein the tube extendsacross the length of the catheter body.

[0039] In most cases, the material of the compliance tube may also beselected to control the compliance of the scoring structure andexpansible shell. Generally, the compliance tube comprises an elasticmaterial, preferably a polymer such as nylon or Pebax™. Alternatively,the compliance tube may comprise a braided material, metal or wire mesh.

[0040] In some aspects of the present invention, the compliance tube mayhave one or more perforations to control the compliance of the scoringstructure and expansible shell. Generally, the perforations comprise oneor more slots extending along the outside circumference of thecompliance tube. The slots may form a pattern along the outsidecircumference of the compliance tube. The slots may be parallel to eachother, and/or extend helically or radially across the circumference ofthe compliance tube. The slots themselves may be formed of a variety ofshapes, such as circular or rectangular.

[0041] Preferably, compliance tube has an outer diameter that tapersfrom its distal end to its proximal end so that the outside diameter atthe proximal end is slightly larger than the inner diameter, and theoutside diameter at the distal end is sized to approximate the diameterof the scoring structure when in a collapsed configuration. This allowsfor the catheter to be readily removed from a vessel without catching orsnagging on the vessel wall. For the tapered configuration, the outerdiameter of the compliance tube will vary depending on the size of thecatheter body and the expansion cage, but the diameter generally tapersdown in the range of 0.004 in to 0.010 in. from the distal end to theproximal end.

[0042] In another aspect of the invention, the attachment structure isconnected at its distal end to the scoring structure and at its proximalend to a manipulator. Typically, the manipulator is positioned at theproximal end of the catheter body and the attachment structure extendsfrom the scoring structure across the length of the catheter body. Inall cases, the attachment structure is capable of axially androtationally extending to accommodate foreshortening of the scoringstructure as the shell is expanded.

[0043] In a preferred embodiment, the attachment structure comprises acompliance tube having an outer diameter and an inner diameter thatextends over the catheter body. Typically, the inner diameter of thecompliance tube is larger than an outer diameter of the catheter body sothat the compliance tube freely extends and rotates with respect to thecatheter body as the scoring structure foreshortens. The compliance ofthe scoring structure and expansible shell may be controlled byadjusting the thickness, length, or material selection of the compliancetube.

[0044] In some embodiments, the compliance of the scoring structure iscontrolled by actuating the manipulator during expansion or contractionof the radially expansible shell. Specifically, the attachment structuremay be axially advanced with respect to the catheter body as the balloonis being inflated or deflated. For example, the attachment structure maybe pulled away from the distal end of the catheter body while theballoon is being expanded to constrain the compliance of balloon.Alternatively, the manipulator may be used to rotate the attachmentstructure with respect to the catheter body to control the compliance ofthe balloon during transition.

[0045] In another embodiment of the present invention, a method ofdilatating a stenosed region in a blood vessel comprises introducing ascoring structure carried over an expansible shell that is connected toa catheter body by an attachment structure, and expanding the scoringstructure within a stenosed region within the blood vessel. In thismethod, the attachment structure axially and/or rotationally extends toaccommodate foreshortening of the scoring structure as the shell isexpanded. The attachment structure generally comprises a compliance tubehaving an outer diameter and an inner diameter that extends over thecatheter body, wherein the inner diameter of the compliance tube islarger than an outer diameter of the catheter body so that thecompliance tube freely extends and rotates with respect to the catheterbody as the scoring structure foreshortens. The thickness, length, andmaterial of the compliance tube may be selected to control thecompliance of the scoring structure and expansible shell.

[0046] In some embodiments, the method further comprises the step offixing the proximal end of the attachment structure to the catheterbody. Alternatively, the method may comprise the step of fixing theproximal end of the attachment structure to a manipulator. In such anembodiment, manipulator is positioned at the proximal end of thecatheter body and the attachment structure extends from the scoringstructure across the length of the catheter body. This allows for thecompliance of the scoring structure and balloon to be controlled byactuating the manipulator during expansion or contraction of theradially expansible shell. Actuation of the manipulator may occur byaxially advancing, pulling or rotating the attachment structure withrespect to the catheter body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIGS. 1, 1A, 1B and 1C are schematic illustrations of the balloonscoring structure embodiment in accordance with an embodiment of theinvention.

[0048]FIG. 2 is a schematic illustration of an exemplary helical scoringstructure embodiment in accordance with embodiments of the invention.

[0049]FIG. 3 is a schematic illustration of an expanded angioplastyballoon carrying a helical scoring structure in accordance withembodiments of the invention.

[0050]FIG. 4 illustrates a scoring structure comprising an alternatingserpentine pattern of intermediate scoring elements between a pair ofend collars.

[0051]FIG. 5 illustrates the serpentine scoring elements of theembodiment of FIG. 4 showed in a rolled-out configuration.

[0052]FIG. 6 illustrates a scoring structure comprising alternatingC-shaped scoring elements between a pair of end collars.

[0053]FIG. 7 illustrates the C-shaped scoring elements of the embodimentof FIG. 6 shown in a rolled-out configuration.

[0054]FIG. 8 is a view of one of the C-shaped scoring elements takenalong line 8-8 of FIG. 6.

[0055]FIG. 9 illustrates an alternative double C-shaped scoring elementwhich could be utilized on a scoring structure similar to thatillustrated in FIG. 6.

[0056]FIG. 10 illustrates an alternative embodiment of a helical scoringstructure comprising serpentine and zigzag structures for mounting ontoa balloon catheter.

[0057]FIG. 11 illustrates a first of the serpentine mounting elements ofthe scoring structure of FIG. 10.

[0058]FIG. 12 illustrates a second of the serpentine mounting elementsof the scoring structure of FIG. 10.

[0059]FIG. 13 illustrates an alternative mounting structure for ahelical or other scoring structure.

[0060]FIG. 14 illustrates the mounting structure of FIG. 13 shown in arolled-out configuration.

[0061]FIG. 15 shows yet another embodiment of a mounting element for thescoring structures of the present invention.

[0062]FIG. 16 illustrates the mounting structure of FIG. 15 shown in arolled-out configuration.

[0063]FIG. 17a illustrates yet another alternative embodiment of acatheter constructed in accordance with the principles of the presentinvention, where an attachment structure is disposed between the scoringstructure and the catheter body.

[0064]FIG. 17b illustrates the structure of FIG. 17a shown without theballoon.

[0065]FIGS. 18a-c illustrate a catheter constructed in accordance withthe principles of the present invention having an attachment structurewith various patterned perforations.

[0066]FIG. 19 illustrates another embodiment of a catheter constructedin accordance with the principles of the present invention having atapered attachment structure.

[0067]FIG. 20 illustrates yet another alternative embodiment of acatheter constructed in accordance with the principles of the presentinvention, where an attachment structure is connected to a manipulator.

DETAILED DESCRIPTION OF THE INVENTION

[0068] In the following description, various aspects of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will also beapparent to one skilled in the art that the present invention may bepracticed without the specific details presented herein. Furthermore,well-known features may be omitted or simplified in order not to obscurethe present invention.

[0069] Embodiments of the present invention relate to device forrevascularization of stenotic vessels and specifically to a ballooncatheter having external elements. The dilatation device comprises aconventional dilatation balloon such as a polymeric balloon and aspiral, or external elements with other configurations mounted on theballoon catheter.

[0070] Reference is now made to FIGS. 1, 1A and 1B, which are schematicillustrations of a dilatation device 10 in accordance with embodimentsof the invention. The dilatation device 10 includes a dilatation balloon12, which may be any conventional angioplasty balloon such as commonlyused by interventional cardiologists or radiologists, and a helical orspiral unit 14 mounted over or attached to dilatation balloon 12. Thecompliance of the balloon and the scoring element(s) should be chosen toassure uniform expansion of the balloon substantially free from“dog-boning” as the combined structure expands within a lesion. If acompliant or a semi-compliant balloon is used and the compliance of thescoring element was not matched to comply with the properties of theballoon, the expansion of the balloon-scoring element system will not beuniform. This non-uniformity may impair the efficacy of the scoringcatheter and, in some cases, may result in poor performance. Forexample, under given pressure, certain parts of the balloon will be ableto expand while other parts will be constrained by excessive resistanceof the scoring elements.

[0071] Helical unit 14 typically made of nitinol. Helical unit 14 may bemade of other metals such stainless steel, cobalt-chromium alloy,titanium, and the like. Alternatively, spiral unit 14 may be a polymericspiral, or made of another elastic material. Helical unit 14 may beattached at its proximal and distal ends to the proximal end 17 anddistal end 18 of dilatation balloon 12. Alternatively, spiral unit 14may be attached to the distal end and/or the proximal end of dilatationballoon 12 by collar-like attachment elements 15 and 16. Spring or othercompliant elements may be alternatively or additionally provided as partof the attachment elements to accommodate shortening of the helical unitas it is expanded.

[0072] Dilatation device 10 is inserted into the vascular system, forexample, using a conventional catheter procedure, to a region ofstenotic material 22 of blood vessel 20. (The term “stenotic” is usedherein to refer to the vascular lesion, e.g., the narrowed portion ofthe vessel that the balloon is meant to open.) At the stenotic area, thedilatation balloon 12 is inflated, for example, by liquid flow into theballoon. Helical unit 14 widens on the inflated dilatation balloon 12.On inflation, the dilatation balloon 12 together with the helical unit14 is pressed against the walls of blood vessel 20 as shown in FIG. 1B.

[0073] Reference is now made to FIG. 1C, illustrating blood vessel 20after the deflation of dilatation balloon 12. Helical unit 14 narrowswhen deflating the dilatation balloon 12, thus the dilatation device 10is narrowed and may be readily retrieved from blood vessel 20. Thedeflation profile of the balloon 10 is low and mainly circular. Thestenotic material 22 in blood vessel 20 is pressed against blood vessel20 walls to widen the available lumen and enhance blood flow. Thepressing of helical unit 14 against the walls of blood vessel 20 causesscoring 23 in the stenotic area.

[0074] Reference is now made to FIG. 3 that shows a scoring structure inthe form of a single wire 24 wrapped around a dilatation balloon 12 in ahelical configuration.

[0075] In other embodiments, the scoring structure of the presentinvention can have a non-helical configuration. Any design of scoringstructure that can accommodate an increase in the diameter of theballoon 12 upon inflation, and return to its configuration when theballoon is deflated, is an appropriate design useful in the invention.At least a portion of the scoring elements will not be parallel to thelongitudinal axis of the balloon catheter to enhance flexibility andimprove scoring.

[0076] Referring again to FIGS. 1A-1C, helical unit 14 is pushedoutwardly by the inflation of the balloon 12, and is stretched by theinflation of the balloon. When the balloon is deflated, helical unit 14assists in the deflation by its elastic recoil. This active deflation isfaster and also leads to a low profile of the deflated balloon. Theballoon 12 is disposed within the helical unit 14, which returns to itspre-inflated shape and forces the balloon to gain a low radial profile.

[0077] In another embodiment of the invention, dilatation device 10 maycarry a stent. The stent can be crimped over the helical unit 14. Inthis way, the helical unit 14 can push the stent against hard areas ofthe lesion, enabling proper positioning of the stent against the vesselwall, even in hard-calcified lesions without pre-dilation.

[0078] Reference is now made to FIG. 2, illustrating the helical unit 14in accordance with embodiments of the invention. Helical unit 14 istypically made of nitinol. Helical unit 14 includes three wires 19 thatare attached to collars 15 and 16 at the proximal end and distal end,respectively. Alternatively the scoring structure may be formed as ametallic cage, which can be made from a slotted tube, or polymeric cageor polymeric external elements.

[0079] Alternatively the scoring structure may comprise wires of otherelements attached directly to the balloon material or close to theballoon ends.

[0080] Wires 19 (FIG. 2) are attached between collars 14 and 15. Thediameter of the wires is typically in the range of 0.05 mm to 0.5 mm.Alternatively, a cage (for example a metallic cage made of a slottedtube) can be used in several configurations that allow local stressconcentrations. The size and shape of the cross section of the cageelements or the cross section of the wires can vary. The cross sectioncan be a circle, rectangle, triangle, or other shape.

[0081] In alternative embodiments, the wires 19 may comprise shortsegments that are attached to the balloon 12.

[0082] In further alternative embodiments of the invention, the helicalunit 14 may be glued, thermally bonded, fused or mechanically attachedat one or both ends to dilatation balloon 12.

[0083] In yet another embodiment, a scoring structure may comprise wiresthat are attached to the dilatation balloon 12 in helical configurationor other configuration. The wires may be thermally attached to theballoon 12, glued, mechanically attached, or the like.

[0084] In still another embodiment, a scoring structure comprises wireor cage elements that are not parallel to the longitudinal axis of theballoon 12 so that the combination of the scoring structure 19 and theballoon 12 remains flexible.

[0085] In additional embodiments, the combination of dilatation balloon12 and scoring structure scores the lesion and provides better vesselpreparation for drug eluting stents by allowing better positioning ofthe stent against the vessel wall and diffusion of the drug through thescores in the lesion.

[0086] In these embodiments, the balloon can be used as a platform tocarry drugs to the lesion where scoring of the lesion can enhancedelivery of the drug to the vessel wall.

[0087] In these embodiments, the balloon can be used for a local drugdelivery by embedding drug capsules, drug containing polymer, and thelike, through the stenotic material and into the vessel wall.

[0088] From the above, it can be seen that the invention comprisescatheters and scoring structures, where the scoring structures arepositioned over the balloons or other expansible shells of the catheter.The scoring structures may be attached directly to the balloons or othershells, in some cases being embedded in the balloon material, but willmore usually be formed as separate cage structures which are positionedover the balloon and attached to the catheter through attachmentelements on either side of the balloon. The expansible cages may beformed using conventional medical device fabrication techniques, such asthose used for fabricating stents, such as laser cutting of hypotube andother tubular structures, EDM forming of hypotubes and tubes, welding ofwires and other components and the like.

[0089] Typically, such expansible shell structures will comprise theattachment elements and an intermediate scoring section between theattachment elements. As illustrated in the embodiments above, theattachment elements may be simple cylindrical or tube structures whichcircumscribe the catheter body on either side of the balloon or otherexpansible shell. The simple tube structures may float over the catheterbody, i.e., be unattached, or may be fixed to the catheter body. Anumber of alternative embodiments for the attachment elements will bedescribed in connections with the embodiments below.

[0090] The intermediate scoring sections may also have a variety ofconfigurations where at least some of the scoring elements willtypically be disposed in a non-axial configuration, i.e., in a directionwhich is not parallel to the axial direction of the expansible cage. Apreferred configuration for the intermediate scoring section comprisesone or more helical elements, generally as illustrated in the priorembodiments. Other exemplary configurations are set forth in theembodiments described below.

[0091] Referring now in particular to FIGS. 4 and 5, an expansiblescoring cage 100 comprises first and second attachment elements 102 and104, respectively, and an intermediate scoring section 106 comprising aplurality of curved serpentine members 110. The serpentine members 110extend circumferentially in opposite directions in an alternatingmanner. This can be understood by observing a “rolled-out” view of theserpentine elements as illustrated in FIG. 5. A second alternativescoring cage structure 120 is illustrated in FIGS. 6-8. The scoring cage120 comprises first and second attachment elements 122 and 124 joined bya spine 126. Plurality of C-shaped scoring elements 128 and 130 areattached to the spine and extend in opposite circumferential directions.The shape of the element can be observed in FIG. 8. The oppositedirections may be observed in the rolled-out view of FIG. 7.

[0092] It will be appreciated that a variety of differentcircumferential structures may be used in place of the C-shapedstructures of FIGS. 6-8. For example, a pair of opposed C-shaped partialring structures may be utilized, as illustrated in FIG. 9. The C-shapedstructures of FIG. 6 or the double C-shaped structures of FIG. 9 canalso be extended so that they wrap around a balloon more than one time,either over or under the spine structure 126.

[0093] The expansible cage structures 100 and 120 will each be mountedover a dilatation balloon, such as the balloon of FIGS. 1-3, with theattachment elements secured to the catheter body on either side of thedilatation balloon. The tube or cylindrical attachment elements 102,104, 122, and 124 may simply float over the catheter body. In otherembodiments, however, it may be desirable to use an adhesive or othermeans for affixing either one or both of the attachment elements to thecatheter body. Having at least one floating attachment element, however,is often desirable since it can accommodate shortening of theintermediate scoring section as that section radially expands. In othercases, however, the individual scoring elements may possess sufficientelasticity to accommodate such shortening. For example, nitinol andother shape memory alloys possess significant stretchability, typicallyon the order of 8% which in some instances will be sufficient toaccommodate any tension applied on the intermediate scoring section byradial expansion of the balloon.

[0094] Referring now to FIGS. 10-12, alternative attachment elements areshown on an embodiment of an expansible scoring cage 140 comprisingthree helical scoring elements 142 which make up the intermediatescoring section. A first attachment element 146 comprises a singleserpentine ring, as best illustrated in FIG. 11 while a secondattachment element 148 comprises a pair of tandem serpentine rings 150and 152, as best illustrated in FIG. 12. The use of such serpentineattachment structures is beneficial since it permits crimping of eitheror both of the structures onto the catheter body in order to fix eitheror both ends of the structure thereto. Usually, the single serpentineattachment structure 48 will be affixed to the catheter body while thedouble serpentine structure will be left free to allow movement of thatend of the scoring cage to accommodate radial expansion of theunderlying balloon.

[0095] Referring now to FIGS. 13 and 14, a further alternativeembodiment of an attachment element useful in the scoring cages of thepresent invention is illustrated. Attachment element 180 includes a pairof serpentine rings 182 and 184, generally as shown in FIG. 12, incombination with a coil spring structure 186 located between said rings182 and 184. The coil spring structure 186 includes three nested coilsprings 190, each joining one of the bend structures 192 and 194 on theserpentine rings 182 and 184, respectively. The structure of the springstructure and adjacent serpentine rings can be understood with referenceto the rolled-out configuration shown in FIG. 14.

[0096] The attachment structure 180 is advantageous since it permits afixed attachment of the outermost ring 182 to the underlying catheterbody while the inner ring 184 remains floating and expansion andcontraction of the intermediate scoring section, comprising helicalelements 196, is accommodated by the coil spring structure 186. Sincethe scoring cage is fixed to the catheter, any risk of loss or slippagefrom the balloon is reduced while sufficient compliance is provided toeasily accommodate radial expansion of the intermediate scoring section.By attaching the structures 180 at at least one, and preferably bothends of the scoring cage, the risk of interference with a stent isreduced.

[0097] Yet another embodiment of the attachment element of the presentinvention includes an axial spring as shown in FIGS. 15 and 16. Theattachment element 200 includes a terminal serpentine ring 202 and anintermediate spring structure 204 including a number of axial serpentinespring elements 206. The nature of the serpentine ring elements 206 canbe observed in the rolled-out configuration of FIG. 16. Optionally, asecond serpentine ring 210 may be provided between the attachmentstructure 200 and the helical scoring elements of the intermediatescoring section 212.

[0098] The embodiments of FIGS. 13-16 comprise spring-like elements 186and 204 to accommodate axial shortening of the scoring structure uponradial expansion. It will be appreciated that other metal and non-metalaxially extensible structures could also be used in such attachmentstructures. For example, elastic polymeric tubes could be attached atone end to the scoring structures and at another end to the catheterbody (or to a ring, collar or other structure which in turn is fixed tothe catheter body).

[0099] Referring now to FIGS. 17a and 17 b, a further embodiment of anangioplasty catheter 250 having an axially distensible attachmentstructure 258 is illustrated. External structure 252 is held overexpansible dilatation balloon 254 and is fixed at one end to the distalend 260 of catheter body 256. The external structure may comprise anystructure typically used for removal of plaque/thrombus from a vesselwall such as a scoring structure, cutting structure or crushingstructure. The proximal end 262 of external structure 252 is connectedto the distal end 264 of attachment structure 258. The proximal end 266of attachment structure 258 is fixed to the catheter body 256. Asdescribed below, the attachment structure 258 may be configured toreduce forces applied on the external structure 252 and the catheterbody 256 during expansion and contraction of balloon 254.

[0100] In a preferred embodiment, attachment structure 258 comprises acylindrical over-tube, or compliance tube, made of an elastic material.Over-tube 258 generally has an inner diameter that is slightly greaterthan the outer diameter of the catheter body 256. Because only a smallsection of the proximal end of the attachment structure 258 is fixed tothe catheter body, the distal end 264 attached to external structure 252is free floating, and is free to slide axially and rotationally withrespect to catheter body 256. Attachment structure 252 may be fixed, forexample by adhesion, directly to the to catheter body 256 and externalstructure 252, or to a collar or other intermediate attachment means.

[0101] As balloon 254 is expanded, external structure 252 expands incircumference and contracts axially along the catheter body 256,creating axial force A on attachment structure 258. Attachment structure258, fixed to the catheter at its end 266, axially stretches toaccommodate the axial movement of the external structure 252. Externalstructure 252 also tends to rotate about the catheter body 256, causinga torsional force T. The distal end 264 of attachment structure 258rotates through the full range of motion of scoring structure 252 toaccommodate torsional force T, while proximal end 266 remains stationarywith respect to catheter body 256.

[0102] The configuration illustrated in FIGS. 17a and 17 b allows thecompliance of the expandable system to be controlled. Generally, whereone end of the scoring structure is free, the compliance of theexpandable system will be a combination of the compliance of the balloonand the scoring structure. However, because the ends of the expandablesystem shown in FIG. 17 are fixed at distal end 260 and proximal end266, the attachment structure controls the compliance of the expandablesystem.

[0103] The compliance of the system may be varied by any combination ofmaterial selection, wall thickness, or length of the over-tube 258.Over-tube 258 may comprise any elastomer, such as elastic polymer likeNylon, Pebax, or PET. Typically, compliance tube 258 is formed fromextruded tubing, but is may also comprise braided polymeric or metallicfibers, or wire mesh. A high memory metal such as nitinol or stainlesssteel may also be used. Where the compliance tube comprises an extrudedpolymeric tube, the wall thickness can vary from 0.01″ to 0.1″, and thelength of the tube can range from 1 cm to 10 cm. For the same material,the thinner-walled and longer the tube, the more compliant the system.

[0104] Referring to FIGS. 18a-c, the compliance of a angioplastycatheter 300 may also be varied by creating one or more perforations incompliance tube 258. The perforations may comprise one or more slots inthe circumference of the tubing. The slots may comprise one continuousslot spiraling across the length of compliance tube 258, or may be anumber of slots aligned in any number of patterns, such as helical 312,or radial 314. The slots may also be any number of shapes, such ascircular or rectangular, and may have a discreet length or be contiguousacross the surface of the compliance tube.

[0105] Referring to FIG. 19, the outside diameter of compliance tube 258maybe tapered to facilitate delivery and retrieval of the scoringcatheter 320 from the treatment site within the lumen. Generally, theouter diameter will be larger at the distal end 264 of the compliancetube 258 and smaller at the proximal end 266 of the compliance tube. Theoutside diameter D₁ at the distal end will vary depending on the profileof the scoring structure and balloon when collapsed but typically rangefrom 0.04″ to 0.01″ larger than the outside diameter D₂ at the proximalend. The outside diameter D₂ at the proximal end is generally as closeas possible to the outside diameter of the catheter body to create asmooth transition between the compliance tube and the catheter. As anexample, for a catheter body having an outside diameter of 0.033″,outside diameter D₁ at the distal end may be 0.042 in with an innerdiameter of 0.038″, the inner diameter providing clearance between thecatheter body so that the distal en of the compliance tube can moverrelative to the catheter body. Correspondingly, the outside diameter D₂at the proximal end may taper down to 0.0345″, with an inner diameter of0.034″ to closely match the catheter body having outside diameter withenough clearance to be bonded to the catheter body by an adhesive.

[0106] The taper may run across the whole length of the compliance tube,or alternatively be only tapered at a section of the length of thecompliance tube. The tapered compliance tube 258 smoothes the transitionbetween the scoring structure and catheter body, and minimizes thelikelihood of the outer tube or scoring structure snagging or catchingon a portion of the luminal wall during delivery or retrieval of thecatheter.

[0107] Now referring to FIG. 20, an alternative embodiment of a scoringcatheter 350 is shown having a manipulator 360. The attachment structure258 is connected at its distal end 264 to the scoring structure 252.Instead of being secured directly to the catheter body 256, the proximalend 266 is attached to manipulator 360. Typically, the manipulator 360is positioned at the proximal end of the catheter body 256 and theattachment structure 258 extends from the scoring structure across thelength of the catheter body. Like the above embodiments, the attachmentstructure is capable of axially and rotationally extending toaccommodate foreshortening of the scoring structure as the shell isexpanded.

[0108] In some embodiments, the compliance of the scoring structure 252and balloon 254 is controlled by actuating the manipulator duringexpansion or contraction of the radially expansible shell. In oneaspect, the attachment structure 258 may be axially advanced withrespect to the catheter body 256 as the balloon is being inflated ordeflated. For example, the attachment structure 258 may be pulled awayfrom the distal end of the catheter body 256 while the balloon 254 isbeing expanded to constrain the compliance of balloon. The attachmentstructure 258 may also be pulled away from the distal end of thecatheter body 256 during or after the balloon 254 is being deflated tominimize the profile of the balloon and scoring structure.Alternatively, the manipulator 360 may be used to rotate the attachmentstructure 258 with respect to the catheter body 256 to control thecompliance of the balloon and scoring structure during transition from acollapsed to expanded state and back to a collapsed state.

[0109] It will be appreciated by persons skilled in the art that thepresent invention is not limited to what has been particularly shown anddescribed hereinabove. Alternate embodiments are contemplated that fallwithin the scope of the invention.

1. An angioplasty catheter comprising: a catheter body having a proximalend and a distal end; a radially expansible shell near the distal end ofthe catheter body; an external structure carried over but unattached tothe shell; and an attachment structure having a proximal end and adistal end attached to the external structure, wherein the attachmentstructure is sufficiently sized and compliant to accommodate geometricalchanges and reaction forces produced by the external structure as it isexpanded by the shell.
 2. A catheter as in claim 1, wherein the externalstructure comprises a scoring structure.
 3. A catheter as in claim 1,wherein the external structure comprises a cutting structure.
 4. Acatheter as in claim 1, wherein at least a portion of the externalstructure is arranged helically over the shell.
 5. A catheter as inclaim 1, wherein the external structure has a proximal end and a distalend, and wherein the proximal end of the attachment structure is fixedto the catheter body and the distal end of the attachment structure issecured to the proximal end of the external structure.
 6. A catheter asin claim 5, wherein the distal end of the external structure is fixed tothe catheter body, and wherein the attachment structure axially extendsto accommodate foreshortening of the external structure as the shell isexpanded.
 7. A catheter as in claim 6, wherein the attachment structurerotationally extends to accommodate rotation of the external structureas the shell is expanded.
 8. A catheter as in claim 7, wherein theattachment structure comprises a compliance tube having an outerdiameter and an inner diameter that extends over the catheter body.
 9. Acatheter as in claim 8, wherein the inner diameter of the compliancetube is larger than an outer diameter of the catheter body so that thecompliance tube freely extends with respect to the catheter body as theexternal structure foreshortens.
 10. A catheter as in claim 9, whereinthe compliance tube inner diameter is sized so that the compliance tubefreely rotates with respect to the catheter body as the externalstructure rotates.
 11. A catheter as in claim 9, wherein the compliancetube is sized to control the compliance of the external structure andexpansible shell.
 12. A catheter as in claim 11, wherein the compliancetube has a wall thickness that is sized to control the compliance of thesystem .
 13. A catheter as in claim 11, wherein the compliance tube hasa length ranging from 1 cm to 10 cm.
 14. A catheter as in claim 9,wherein the material of the compliance tube is selected to control thecompliance of the external structure and expansible shell.
 15. Acatheter as in claim 14, wherein the compliance tube comprises anelastic material.
 16. A catheter as in claim 15, wherein the compliancetube comprises a polymer selected from the group consisting of nylon orPebax.
 17. A catheter as in claim 15, wherein the compliance tubecomprises a braided material.
 18. A catheter as in claim 15, wherein thecompliance tube comprises a metal.
 19. A catheter as in claim 18,wherein the compliance tube comprises a wire mesh.
 20. A catheter as inclaim 9, wherein the compliance tube has one or more perforations tocontrol the compliance of the external structure and expansible shell.21. A catheter as in claim 20, wherein the one or more perforationscomprise one or more slots extending along the outside circumference ofthe compliance tube.
 22. A catheter as in claim 21, wherein the slotsform a pattern along the outside circumference of the compliance tube.23. A catheter as in claim 22, wherein the slots are parallel to eachother.
 24. A catheter as in claim 22, wherein the slots extend helicallyacross the compliance tube.
 25. A catheter as in claim 22, wherein theslots extend radially across the compliance tube.
 26. A catheter as inclaim 22, wherein the slots are circular in shape.
 27. A catheter as inclaim 22, wherein the slots are rectangular in shape.
 28. A catheter asin claim 8, wherein the compliance tube has an outer diameter thattapers from its distal end to its proximal end.
 29. A catheter as inclaim 28, wherein the outer diameter of the compliance tube tapers downfrom the distal end and to the proximal end so that the outside diameterat the proximal end closely matches the diameter of the catheter body.30. A external catheter as in claim 1, wherein the attachment structureis connected at its distal end to the external structure and at itsproximal end to a manipulator.
 31. A catheter as in claim 30, whereinthe manipulator is positioned at the proximal end of the catheter bodyand the attachment structure extends from the external structure acrossthe length of the catheter body.
 32. A catheter as in claim 30, whereinthe attachment structure axially extends to accommodate foreshorteningof the external structure as the shell is expanded.
 33. A catheter as inclaim 32, wherein the attachment structure rotationally extends toaccommodate rotation of the external structure as the shell is expanded.34. A catheter as in claim 33, wherein the attachment structurecomprises a compliance tube having an outer diameter and an innerdiameter that extends over the catheter body.
 35. A catheter as in claim34, wherein the inner diameter of the compliance tube is larger than anouter diameter of the catheter body so that the compliance tube freelyextends and rotates with respect to the catheter body as the externalstructure foreshortens.
 36. A catheter as in claim 35, wherein thecompliance tube has a wall thickness and a length that are sized tocontrol the compliance of the external structure and expansible shell.37. A catheter as in claim 35, wherein the compliance of the externalstructure is controlled by actuating the manipulator during expansion ofthe radially expansible shell.
 38. A catheter as in claim 35, whereinthe compliance of the external structure is controlled by actuating themanipulator during contraction of the radially expansible shell.
 39. Acatheter as in any of claims 37 or 38, wherein actuating the manipulatorcomprises axially advancing the attachment structure with respect to thecatheter body.
 40. A catheter as in claim 39, wherein axially advancingthe attachment structure comprises pulling the attachment structure awayfrom the distal end of the catheter body.
 41. A catheter as in any ofclaims 37 or 38, wherein actuating the manipulator comprises rotatingthe attachment structure with respect to the catheter body.
 42. A methodof dilatating a stenosed region in a blood vessel, the methodcomprising: introducing an external structure carried over an expansibleshell that is connected to a catheter body by an attachment structure;expanding the external structure within a stenosed region within theblood vessel, wherein the attachment structure axially extends toaccommodate foreshortening of the external structure as the shell isexpanded.
 43. A method as in claim 42, wherein the attachment structurerotationally extends to accommodate rotation of the external structureas the shell is expanded.
 44. A method as in claim 43, wherein theattachment structure comprises a compliance tube having an outerdiameter and an inner diameter that extends over the catheter body. 45.A method as in claim 44, wherein the inner diameter of the compliancetube is larger than an outer diameter of the catheter body so that thecompliance tube freely extends and rotates with respect to the catheterbody as the external structure foreshortens.
 46. A method as in claim44, wherein the compliance tube is sized to control the compliance ofthe external structure and expansible shell.
 47. A method as in claim46, wherein sizing the compliance tube comprises sizing the wallthickness of the compliance tube.
 48. A method as in claim 46, whereinthe compliance tube has a length ranging from 1 cm to 10 cm.
 49. Amethod as in claim 44, wherein the material of the compliance tube isselected to control the compliance of the external structure andexpansible shell.
 50. A method as in claim 49, wherein the compliancetube comprises an elastic material.
 51. A method as in claim 50, whereinthe compliance tube comprises a polymer.
 52. A method as in claim 43,wherein the external structure has a proximal end and a distal end, andwherein the method further comprises the step of fixing the proximal endof the attachment structure to the catheter body.
 53. A method as inclaim 43, wherein the external structure has a proximal end and a distalend, and wherein the method further comprises the step of fixing theproximal end of the attachment structure to a manipulator.
 54. A methodas in claim 53, wherein the manipulator is positioned at the proximalend of the catheter body and the attachment structure extends from theexternal structure across the length of the catheter body.
 55. A methodas in claim 54, wherein the compliance of the external structure iscontrolled by actuating the manipulator during expansion of the radiallyexpansible shell.
 56. A method as in claim 54, wherein the compliance ofthe external structure is controlled by actuating the manipulator duringcontraction of the radially expansible shell.
 57. A method as in any ofclaims 55 or 56, wherein actuating the manipulator comprises axiallyadvancing attachment structure with respect to the catheter body.
 58. Amethod as in claim 57, wherein axially advancing attachment structurecomprises pulling the attachment structure away from the distal end ofthe catheter body.
 59. A method as in any of claims 55 or 56, whereinactuating the manipulator comprises rotating the attachment structurewith respect to the catheter body